Offline installer do not require any temporary space.

Though not a real fix, it is still part of QTIFW-395.

Change-Id: Idcde0dbd6b578fe900fc3ea3f11a68a90ff1f122
Reviewed-by: Tim Jenssen <tim.jenssen@digia.com>
Reviewed-by: Niels Weber <niels.weber@digia.com>